Abstract
Pu-erh tea undergoes a unique fermentation process and contains theabrownins, polysaccharides and caffeine; although it is unclear about which component is associated with the down regulation of nitric oxide levels or how this process is mediated. To address this question we examined the effects of pu-erh tea on nitric oxide synthase (NOS) genes. Cohorts of rats were separately given four-week treatments of water as control, pu-erh tea, or the tea components: theabrownins, caffeine or polysaccharides. Five experimental groups were injected with lipopolysaccharides (LPS) to induce nitric oxide (NO) production, while the corresponding five control groups were injected with saline as a negative control. The serum and liver NO concentrations were examined and the NOS expression of both mRNA and protein was measured in liver. The results showed that the rats which were fed pu-erh tea or polysaccharides had lower levels of NO which corresponded with the down-regulation of inducible nitric oxide synthase (iNOS) expression. We further demonstrate that this effect is mediated through reduction of Toll-like receptor 4 (TLR4) signaling. Thus we find that the polysaccharide components in pu-erh tea reduce NO levels in an animal model by inhibiting the iNOS expression via signaling through TLR4.
Highlights
Nitric oxide (NO) is a free radical which is produced by nitric oxide synthase (NOS) in the body.Three NOS isoforms have been identified, neural nitric oxide synthase, endothelial nitric oxide synthase and inducible nitric oxide synthase. nNOS and eNOS are constitutive, whereas iNOS is inducible in response to various stimuli, such as lipopolysaccharides (LPS) which can activateToll-like receptor 4 (TLR4) signal pathway [1,2]
We demonstrated for the first time that the unique polysaccharides in pu-erh tea exerted an inhibitory effect on iNOS expression by reducing the activity of TLR4, which is the initiative molecule of the iNOS expression signal pathway
One third (33.13 ± 3.18%) of pu-erh tea consisted of polyphenols, of which theabrownins represented a significant fraction (7.32–10.50%)
Summary
Nitric oxide (NO) is a free radical which is produced by nitric oxide synthase (NOS) in the body. Excess NO generation should be avoided and foods that aid in inhibiting the pro-inflammatory NF-κB-mediated iNOS activity may offer a potential health benefit. Studies of the possible health benefits on pu-erh tea have shown a wide range of biological effects, such as antioxidative [10,11], antiobesity [12,13], antihyperlipidemic [14], antimutagenic [15], and antimicrobial [15]. Additional components of pu-erh tea are indispensable for its health benefit, such as polysaccharides and caffeine [19]. We demonstrated for the first time that the unique polysaccharides in pu-erh tea exerted an inhibitory effect on iNOS expression by reducing the activity of TLR4, which is the initiative molecule of the iNOS expression signal pathway.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
